JP2013156091A - Method for measuring linear elastic modulus, and linear elastic modulus measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a linear elastic modulus capable of reducing influences of disturbance such as vibration and electrical noise and, even when damping due to viscosity stress is high, capable of highly accurately and stably measuring the linear elastic modulus of a linear elastic body, and provide a linear elastic modulus measuring apparatus.SOLUTION: A linear elastic modulus measuring apparatus 100 computes a vibration velocity dx/dt of a vibrating body 1 from displacement of the vibrating body 1 that has been placed in contact with a linear elastic body, multiplies the dx/dt by a linear velocity feedback gain Gto generate a feedback control signal Fs and applies force Fv proportional to the vibration velocity of the vibrating body 1 to the vibrating body 1 using the Fs to cause the vibrating body 1 to undergo self-excited vibration. A linear elastic modulus kof the linear elastic body is computed from a frequency fwhen self-excited vibration of the vibrating body 1 is detected and a mass (M) of the vibrating body 1.

Description

  The present invention relates to a technique for measuring the elastic modulus of a linear elastic body, and in particular, in a dynamic system in which a viscous stress is generated together with an elastic force, a linear elastic modulus measuring method effective for reducing the influence of damping due to the viscous stress. And a linear elastic modulus measuring apparatus.

  Conventionally, the elastic modulus of a linear elastic body is measured by applying a static strain to the elastic body and calculating the elastic modulus by measuring the stress, or by forcing the linear elastic body to vibrate and resonance frequency. A method of calculating the elastic modulus from the above is known. About these measuring methods, it describes in the nonpatent literature 1, for example.

"IIC REVIEW / 2010/4. No.43 P30-34 (IHI Inspection and Measurement Co., Ltd.)"

Among the above-mentioned conventional technologies, the method of measuring the elastic modulus by applying a static strain to the elastic body is easily affected by disturbances such as vibration and electrical noise, and realizes highly accurate and stable measurement. It was difficult. In particular, it was difficult to apply to viscoelastic bodies.
In addition, the method of calculating the elastic modulus from the resonance frequency by forcibly applying vibrations is particularly ambiguous when the damping due to viscous stress is large. It has been difficult to accurately determine the resonance frequency.
The present invention solves the above-mentioned problems in the method of measuring the elastic modulus of a linear elastic body, is less affected by disturbances such as vibration and electrical noise, and is highly accurate and stable linear elasticity even when damping due to viscous stress is large. It is an object of the present invention to provide a linear elastic modulus measuring method and a linear elastic modulus measuring apparatus capable of measuring a modulus.

[Mode 1] In order to achieve the above object, a linear elastic modulus measurement method according to mode 1 includes a vibrating body that is brought into contact with an object to be measured, an actuator that self-excites the vibrating body, and a vibration speed of the vibrating body. The vibration speed detection means for detecting the vibration speed positively feedback the vibration speed detected by the vibration speed detection means,
Fs = G _lin · (dx / dt)
Where Fs: feedback control signal
G _lin : Positive linear velocity feedback gain
dx / dt: feedback control means for feedback-controlling the actuator by a feedback control signal expressed by a vibration speed of a vibrating body, and a linear elastic modulus measuring method using a linear elastic modulus measuring device, Changing the linear velocity feedback gain in the control; detecting whether the vibrator is self-excited; and
Calculating a linear elastic modulus of the object to be measured based on a vibration frequency when it is detected that the vibrating body is self-excited.

[Embodiment 2] Furthermore, in the method for measuring the linear elastic modulus of the embodiment 2, in the step of calculating the linear elastic modulus for the configuration of the embodiment 1, the mass of the vibrating body is M, and the vibration frequency of the vibrating body is When f _s , the linear elastic modulus k _lin of the measurement object is
k _lin = ω _s ² × M
However, ω _s : 2π × f _s
And the vibration frequency when it is detected that the vibration body has self-excited vibration is applied as the vibration frequency f _s .

  [Mode 3] Furthermore, in the linear elastic modulus measurement method according to mode 3, the linear elastic modulus measurement apparatus includes a displacement detection unit that detects the displacement x of the vibrating body, with respect to the configuration of mode 1 or 2. Including pre-vibrating the vibrating body at a constant frequency when the displacement x in an initial stage when the vibrating body starts self-excited vibration is below a detection lower limit value of the displacement detecting means. It is said.

[Mode 4] On the other hand, in order to achieve the above object, a linear elastic modulus measuring apparatus according to mode 4 includes a vibrating body that is brought into contact with a measurement object, an actuator that self-excites the vibrating body, and vibrations of the vibrating body. Vibration speed detection means for detecting speed, and positive feedback of the vibration speed detected by the vibration speed detection means,
Fs = G _lin · (dx / dt)
Where Fs: feedback control signal
G _lin : Positive linear velocity feedback gain
dx / dt: feedback control means for feedback-controlling the actuator by a feedback control signal represented by vibration speed of the vibration body, gain adjustment means for changing the linear speed feedback gain in the feedback control, and the vibration body Self-oscillation detecting means for detecting whether or not excitation vibration has occurred, and based on the vibration frequency when the self-excited vibration detection means determines that the vibration body has detected self-excited vibration. Linear elastic modulus calculating means for calculating the linear elastic modulus.

With such a configuration, the vibration speed dx / dt of the vibrating body is detected by the vibration speed detection means, and the detected vibration speed dx / dt is multiplied by the linear speed feedback gain G _lin by the feedback control means. The actuator is feedback controlled by the feedback control signal Fs = G _lin · (dx / dt). When the actuator is feedback-controlled, a force proportional to the vibration speed of the vibrating body is applied to the vibrating body in contact with the measurement object by the actuator. The linear velocity feedback gain is changed by the gain adjusting means, and on the other hand, it is detected by the self-excited oscillation detecting means whether or not the vibrating body has self-excited. When the self-excited oscillation detecting means detects that the self-excited vibration is detected, the linear elastic modulus calculating means calculates the linear elastic modulus of the measurement object based on the vibration frequency at the time of detecting the self-excited vibration.

  As described above, according to the present invention, when a vibrating body that is in contact with a measurement object is subjected to a force proportional to the vibration speed of the vibrating body to cause the vibrating body to self-excited and self-excited. The linear elastic modulus of the measurement object is calculated based on the vibration frequency. Thereby, even when the damping due to the viscous stress of the measurement object is large, it is possible to measure a highly accurate and stable linear elastic modulus. Therefore, by applying the present invention to a rheometer or the like, the elastic modulus of a viscous viscoelastic body can be measured with high accuracy. In addition, for example, it is possible to realize a device that measures the hardness of a measurement object such as an internal organ with high accuracy.

It is a schematic diagram of the dynamic system for demonstrating the relationship between the linear elastic body which concerns on embodiment of this invention, a vibrating body, an actuator, and a displacement sensor. (A) is a figure which shows an example of the frequency response curve of three types of linear elastic bodies from which the viscous stress in the conventional measuring method differs, (b) is a frequency response curve at the time of using the measuring method of this invention. It is a figure which shows an example. It is a schematic structure figure showing an example of a linear elastic modulus measuring device concerning an embodiment of the present invention. It is a flowchart which shows an example of the process sequence of a linear elastic modulus measurement process. It is a figure which shows an example of an apparatus structure at the time of applying the linear elastic modulus measuring apparatus 100 of this embodiment to the thin film material which is a measuring object.

Hereinafter, embodiments of a linear elastic modulus measuring method and a linear elastic modulus measuring device according to the present invention will be described with reference to the drawings. 1 to 5 are diagrams showing an embodiment of a linear elastic modulus measuring method and a linear elastic modulus measuring apparatus according to the present invention.
(Constitution)
FIG. 1 is a schematic diagram of a dynamic system for explaining the relationship among a linear elastic body, a vibrating body, an actuator, and a displacement sensor according to an embodiment of the present invention.
The linear elastic modulus measurement method of the present embodiment includes an actuator for applying force to a linear elastic body, a displacement sensor for measuring displacement, and a conversion circuit for differentiating the signal of the displacement sensor and converting it into force output. And a linear elastic modulus measuring device including a measuring device for measuring the vibration frequency.

Here, the linear elastic body having both elasticity and viscosity can be replaced with a dynamic system having a spring and a dashpot. As a model of such a dynamic system, a Maxwell model in which a spring and a dashpot are connected in series and a Kelvin-Forked model in which a spring and a dashpot are connected in parallel are known. The example shown in FIG. 1 is an example in which the Kelvin-Forked model is applied. In the dynamic model of FIG. 1, the linear elastic body that is a measurement object is expressed as a configuration in which a spring having a linear elastic modulus k _lin and a dashpot having a viscosity C _lin are connected in parallel.

In the present embodiment, a force is applied to the linear elastic body via a vibrating body having a mass M, and therefore, as shown in FIG. It is expressed as a dynamic model of a spring, mass (mass), and dashpot system with vibrating bodies connected. Specifically, the vibrating body is brought into contact with the linear elastic body, and a force F is applied to the vibrating body from the actuator to displace the vibrating body (self-excited vibration), and the displacement of the vibrating body is detected by a displacement sensor. . For example, a force F in the shearing direction (shear deformation direction) is applied to the linear elastic body via the vibrating body, and the displacement in the shearing direction is detected.
The contact referred to here corresponds to, for example, close contact of the vibrating body with the measurement object if the measurement object is semi-solid, depending on the physical properties of the measurement object. For example, if the measurement object is a fluid, for example, inserting a vibrating body such as a cantilever into the fluid is applicable.

In such a configuration, when a force F is applied to a linear elastic body (strictly, a vibrating body), the displacement follows a motion equation such as the following equation (1).
M (d ² x / dt ² ) + c _lin (dx / dt) + k _lin x = F (1)
In the above equation (1), M is the mass of the vibrating body, C _lin is the proportional coefficient of the viscosity term, k _lin is the linear elastic modulus, and x is the displacement of the linear elastic body (same as the displacement of the vibrating body). In this embodiment, a force F (hereinafter referred to as Fv) proportional to the motion speed is applied to the linear elastic body. In this case, the equation of motion is as shown in the following equation (2).
M (d ² x / dt ² ) + c _lin (dx / dt) + k _lin x = G _lin (dx / dt) (2)

Here, G _lin in the above equation (2) is a proportional coefficient between input force and speed, and is hereinafter referred to as a linear speed feedback gain. When the right side of the above equation (2) is shifted to the left side, the following equation (3) is obtained.
M (d ² x / dt ² ) + (c _lin −G _lin ) (dx / dt) + k _lin x = 0
... (3)
When the linear velocity feedback gain G _lin becomes larger than the proportional constant C _lin of the viscosity term, a negative viscosity term is generated, and self-oscillation occurs in the linear elastic body. The vibration angular frequency at this time can be expressed by the following equation (4).
ω _s = (k _lin / M) ^1/2 (4)
Here, ω _s in the above equation (4) is an angular frequency of vibration (self-excited vibration) generated by self-excited oscillation. If the vibration angular frequency ω _s of self-excited oscillation can be measured from the above equation (4), the linear elastic modulus k _lin can be calculated by the following equation (5) obtained by _modifying the above equation (4).
k _lin = ω _s ² × M (5)

  Next, problems of the conventional measurement method using the resonance method will be described with reference to FIG. FIG. 2A is a diagram showing an example of frequency response curves of three types of linear elastic bodies having different viscous stresses in the conventional measurement method, and FIG. 2B is a frequency when the measurement method of the present invention is used. It is a figure which shows an example of a response curve. In FIG. 2, the vertical axis represents the amplitude of the linear elastic body, and the horizontal axis represents the vibration angular frequency of the linear elastic body.

As in the prior art, when a sinusoidal forced excitation force F = Fosin ω _t (where Fo is the amplitude of the excitation force) is given to the linear elastic body, the linear elastic body has x = A sin (ω _t + φ). As shown in FIG. Here, A is the displacement amplitude, and φ is the phase. The amplitude A changes as shown in FIG. 2A according to the angular frequency of the forced excitation force F. This frequency response curve varies depending on the magnitude of the viscous stress. When the viscous stress is small, the Q value becomes large, and the frequency response curve has a sharp peak as shown by the curve CL1 in FIG. The angular frequency ω _o of this peak can be approximately calculated by ω _o = (k _lin / M) ^1/2 , and the linear elastic modulus k _lin can be calculated from this equation. However, when the viscous stress is increased, the Q value is decreased according to the magnitude, and the approximation cannot be established. In addition, as indicated by a curve CL2 in FIG. 2A, the peak becomes gentle and it is difficult to determine the peak position. Further, when the viscous stress becomes larger and the Q value becomes smaller, the viscous stress exceeds the overdamping condition, and the peak itself does not exist as shown by the curve CL3 in FIG. .

On the other hand, in the method for measuring the linear elastic modulus of the present invention, the force F applied to the linear elastic body is a force Fv proportional to the velocity of the linear elastic body. Therefore, self-oscillation occurs in the linear elastic body, and the angular frequency is ω _s = (k _lin / M) ^1/2 as shown in the above equation (4). When this is represented by a frequency response curve, as shown in FIG. 2B, a curve having a sharp peak only at ω _s is obtained. This curve is independent of viscous stress. Therefore, the linear elastic modulus k _lin can be measured from the angular frequency ω _s of self-excited oscillation without being affected by the magnitude of the viscous stress.

Next, a schematic configuration of the linear elastic modulus measuring apparatus according to the present embodiment will be described based on FIG. FIG. 3 is a schematic configuration diagram illustrating an example of a linear elastic modulus measuring apparatus according to the present embodiment.
As shown in FIG. 3, the linear elastic modulus measuring apparatus 100 according to the present embodiment includes a vibrating body 1, a displacement sensor 2, a displacement detector 3, a vibration speed calculator 4, a gain adjusting means 5a, and an amplifier. 5b, the actuator 6, the driver 7, the frequency detection part 8, the self-excited oscillation detection means 9, and the calculator 10 are comprised.

The vibrating body 1 is a structure having a mass M made of a semiconductor material or the like, and the material, shape, and the like thereof vary depending on the physical properties of the linear elastic body to be measured. Further, when measuring the linear elastic modulus k _lin of the linear elastic body, the vibrating body 1 is brought into contact with the linear elastic body. If the linear elastic body is a thin film material such as a coating agent, for example, the vibrating body 1 is a structure having a rectangular cross section (for example, a cube), and one surface thereof is brought into close contact with the thin film. If the linear elastic body is a fluid, the vibrating body 1 has a cantilever shape such as a cantilever, and the probe portion is inserted into the fluid.

The displacement sensor 2 is a sensor for detecting the displacement of the vibrating body 1 and supplies the sensor output to the displacement detector 3.
The displacement detector 3 detects the displacement x of the vibrating body 1 based on the sensor output from the displacement sensor 2 and sends the detected displacement x to the vibration speed calculator 4, the frequency detector 8, and the self-excited oscillation detector 9. Supply.
In addition, as a combination of the displacement sensor 2 or the displacement sensor 2 and the displacement detector 3, a capacitance displacement sensor, an encoder, an optical displacement meter, a strain gauge, etc. can be used, for example.

The vibration speed computing unit 4 includes a differentiator, calculates the vibration speed dx / dt of the vibrating body 1 by differentiating the displacement x from the displacement detector 3 with the differentiator, and the calculated dx / dt is an amplifier. 5b.
The gain adjusting means 5a sets an initial value of the linear velocity feedback gain G _lin of the amplifier 5b, and based on a signal (described later) indicating that the self-excited oscillation is detected from the self-excited oscillation detecting means 9 The gain G _lin of 5b is changed. Specifically, every time a signal indicating that no self-excited oscillation is detected is received from the self-excited oscillation detecting means 9, the previous gain is increased (or decreased) by a preset Δg. This gain adjustment is repeated until the self-excited oscillation of the vibrating body 1 is detected by the self-excited oscillation detecting means 9.

The amplifier 5b includes a variable amplifier, and multiplies the linear speed feedback gain G _lin set by the gain adjusting means 5a by the vibration speed dx / dt supplied from the vibration speed calculator 4. Then, the amplifier 5b supplies the calculated G _lin · dx / dt to the driver 7 as the feedback control signal Fs.
The actuator 6 applies a force Fv proportional to the motion speed of the vibrating body 1 to the vibrating body 1 based on the drive signal supplied from the driver 7. As the actuator 6, for example, a piezoelectric element, a voice coil motor, an electrostatic actuator, or the like can be used.

Based on the feedback control signal Fs supplied from the amplifier 5b, the driver 7 generates a drive signal that drives the actuator 6 so as to apply a force Fv proportional to the motion speed of the vibrating body 1 to the vibrating body 1. A drive signal is supplied to the actuator 6. For example, a drive signal obtained by amplifying the feedback control signal Fs is supplied to the actuator 6.
The frequency detector 8 detects the frequency of the vibration waveform composed of the displacement x based on the displacement x of the vibrating body 1 supplied from the displacement detector 3. Then, the frequency detection unit 8 supplies the detected frequency f _s to the calculator 10.

As the frequency detection unit 8, for example, a frequency counter, an FFT analyzer, a spectrum analyzer, or the like can be used.
The self-excited oscillation detecting means 9 detects whether or not the vibrator 1 is self-oscillating based on the vibration displacement x (or the vibration speed dx / dt or the frequency spectrum of the vibration amplitude). When the self-excited oscillation detecting means 9 detects that self-excited oscillation is occurring, the self-excited oscillation detecting means 9 supplies a signal indicating the detection to the gain adjusting means 5a and the computing unit 10, respectively.

On the other hand, when detecting that the self-excited oscillation is not occurring, the self-excited oscillation detecting means 9 supplies a signal indicating the detection to the gain adjusting means 5a.
The computing unit 10 responds to a signal indicating that self-excited oscillation has been detected, a frequency f _s at the time of detecting self-excited oscillation (hereinafter referred to as an oscillation frequency f _s ), and a preset mass M of the vibrator 1. Based on the above, the linear elastic modulus k _lin of the measurement object is calculated according to the above equation (5). Specifically, the oscillation angular frequency ω _s is calculated by multiplying the oscillation frequency f _s by 2π. Furthermore, it calculates the omega _s ² by squaring the oscillation angular frequency omega _s, by multiplying the mass M to omega _s ^2, calculates the linear elastic modulus k _lin.

When calculating the linear elastic modulus k _lin in the calculator 10, the linear velocity feedback gain G _lin at the time of detecting self-excited oscillation by the gain adjusting means 5 a is set to G _lin + Δg 2 (Δg 2 is a preset increase) Adjust). Further, the feedback control signal Fs supplied from the amplifier 5b to the driver 7 is maintained at (G _lin + Δg2) · dx / dt. Then, the frequency detector 8 may obtain the frequency f _{s of the} vibration waveform composed of the vibration displacement x at this time, and the calculator 10 may calculate the linear elastic modulus k _lin using this f _s. Good.

Further, although not shown, the linear elastic modulus measuring apparatus 100 of the present embodiment includes a computer system for realizing the above functions on software or for controlling hardware for realizing the functions. Yes.
Specifically, a CPU (Central Processing Unit) responsible for various controls and arithmetic processing, a RAM (Random Access Memory) responsible for work memory, and a dedicated program for realizing the above functions and program execution are required. ROM (Read Only Memory) for storing various data and the like, and a data transmission bus for transmitting data to each component.

(Linear elastic modulus measurement process)
Next, based on FIG. 4, the process procedure of the linear elasticity measurement process performed in the linear elasticity measurement apparatus 100 is demonstrated. FIG. 4 is a flowchart illustrating an example of a processing procedure of linear elastic modulus measurement processing.
As shown in FIG. 4, first, the process proceeds to step S100, and the linear velocity feedback gain G _lin of the amplifier 5b is set to an initial value in the gain adjusting means 5a. Thereafter, the process proceeds to step S102. This initial value can be arbitrarily set, for example, zero.
In step S102, the self-excited oscillation detecting means 9 determines whether or not the vibrating body 1 has vibrated (self-excited oscillation). If it is determined that the vibrating body 1 has vibrated (Yes), a signal indicating that vibration has been detected is output. Then, the operation unit 10 is supplied to the arithmetic unit 10, and the process proceeds to step S104. On the other hand, if it is determined that there is no vibration (No), a signal indicating that the vibration is not detected is supplied to the gain adjusting means 5a, and the process proceeds to step S108.

  Here, whether or not the vibrating body 1 vibrates is determined, for example, when the vibration displacement x or the vibration speed dx / dt changes by a predetermined threshold value or more to determine that the vibrating body 1 has vibrated. You can do it. Further, the frequency spectrum of the vibration amplitude of the vibrating body 1 is obtained by performing FFT (Fast Fourier Transform) processing on the vibration displacement data including the vibration displacement x, and the spectrum of the single oscillation frequency is generated. Sometimes, it may be determined that the vibrating body 1 has vibrated.

When the process proceeds to step S104, the computing unit 10 obtains the oscillation frequency f _s from the frequency detection unit 8 in accordance with the signal indicating that the vibration from the self-excited oscillation detection means 9 is detected, and the process proceeds to step S106. To do.
In step S106, the calculator 10 calculates the oscillation angular frequency omega _s from acquired oscillation frequency f _s in step S104, calculates the omega _s ² by squaring the oscillation angular frequency omega _s. Furthermore, this ω _s ² is multiplied by the mass M of the vibrating body 1 to calculate the linear elastic modulus k _lin , and the series of processes is completed.

On the other hand, if the vibration (self-excited oscillation) is not detected in step S102 and the process proceeds to step S108, it indicates that the gain adjusting means 5a detects that no vibration is generated from the self-excited oscillation detecting means 9. In response to the signal, the current linear velocity feedback gain G _lin set in the amplifier 5b is increased by a preset Δg. Thereafter, the process proceeds to step S102. The linear velocity feedback gain G _lin may be continuously changed or may be changed for each preset change amount.

That is, until it is determined in step S102 that the vibrating body 1 has vibrated, the processes of step S102 and step S108 are repeated to increase the linear velocity feedback gain G _lin , and the step is performed when the vibrating body 1 vibrates. The process moves from S102 to step S104. Then, the vibration frequency of the vibrating body 1 at this time is acquired as the oscillation frequency f _s .

Note that “Δg” is a relatively small value such that the oscillation frequency f _s can be detected from the vibration displacement x of the vibrating body 1 when the linear velocity feedback gain G _lin is maintained at “G _lin + Δg”. Set. As “Δg” increases, the linear velocity feedback gain G _lin increases and the vibration amplitude of the vibrating body 1 increases. As a result, the oscillation frequency f _s of the vibrating body 1 deviates from the linear natural frequency, and the oscillation frequency f _s tends to vary depending on a slight change in vibration amplitude. That is, the detection error of ω _{s in} the above equation (5) becomes large, and the calculation accuracy of the linear elastic modulus k _lin decreases. Therefore, “Δg” is preferably as small as possible.

(Operation)
Next, based on FIG. 5, operation | movement of the linear elastic modulus measuring apparatus 100 of this embodiment is demonstrated.
FIG. 5 is a diagram illustrating an example of a device configuration of the linear elastic modulus measuring apparatus 100 when the linear elastic modulus measuring method of the present embodiment is applied to a thin film material that is an object to be measured.
As shown in FIG. 5A, the linear elastic body as a measurement object is a thin film material adhered on a fixed substrate, and the vibrating body 1 having a mass M is in close contact therewith. The vibrating body 1 has a configuration in which a cubic structure 1b having a mass M is provided at one end of a rod-like body 1a such as a needle, and the lower end surface of the structure 1b is in close contact with the thin film material. ing. In the example of FIG. 5, a voice coil motor is employed as the actuator 6 for self-excited vibration of the vibrating body 1, and the force Fv can be applied in the direction in which the thin film material shears by the voice coil motor. ing.
For example, when the force Fv is applied in the direction shown in FIG. 5A, the displacement of the vibrating body 1 due to the force Fv causes shear deformation in the displacement direction shown in FIG.

Note that by using a voice coil motor as the actuator 6, it is possible to apply a force Fv to the vibrating body 1 in a non-contact manner. The displacement x of the vibrating body 1 is detected using a capacitance displacement meter (corresponding to the displacement sensor 2 and the displacement detector 3). The detected displacement signal (displacement x) is input to the vibration speed calculator 4 connected to the capacitance displacement meter, where the vibration speed dx / dt of the vibrating body 1 is calculated. The calculated dx / dt is input to the amplifier 5b, where the vibration speed dx / dt is multiplied by the linear speed feedback gain _Glin , and the calculated _Glin · dx / dt is used as the feedback control signal Fs to obtain the voice coil. This is supplied to the motor control circuit (corresponding to the driver 7). The displacement signal from the capacitance displacement meter is input to a frequency counter (corresponding to the frequency detection unit 8) connected to the capacitance displacement meter, and the vibration frequency f _s of the vibrating body 1 is detected.

Hereinafter, the operation of the linear elastic modulus measuring apparatus 100 having the apparatus configuration shown in FIG.
First, before the measurement, the mass M of the vibrating body 1 is accurately measured, and the measured mass M is stored in a memory (RAM or the like). If the mass M of the structure 1b provided at one end of the rod-shaped body 1a is sufficiently larger than the mass of the rod-shaped body 1a, the mass M may ignore the mass of the rod-shaped body 1a. However, more accurate linear elastic modulus can be measured by considering the mass of the rod-shaped body 1a. The mass M stored in the memory is used in the computing unit 10 when detecting self-excited oscillation.

Next, the linear speed feedback gain G _lin of the amplifier 5b is set to an initial value (small value) by the gain adjusting means 5a (step S100), and the power switch of each component device is turned on. Thereby, measurement is started.
Here, in the initial stage of the measurement start, since the vibrating body 1 is not displaced, the displacement x detected by the capacitance displacement meter is “0”, and the vibration speed dx / dt is also “0”. However, in reality, the displacement x does not become “0” due to the noise of the surrounding environment or the like, and has some value. Accordingly, the displacement x is detected by the capacitance displacement meter, and the vibration speed calculator 4 calculates the vibration speed dx / dt from the displacement x. The vibration speed dx / dt is supplied to the amplifier 5b, and the set linear speed feedback gain G _lin and dx / dt are multiplied, and G _lin · dx / dt as the multiplication result is used as the feedback control signal Fs. Input to the control circuit of the voice coil motor.
In the initial stage of self-excited oscillation, if the displacement of the vibrating body 1 falls below the lower limit of detection of the capacitance displacement meter only with ambient noise or the like, vibration of an arbitrary frequency is given in advance. That is, the vibrating body 1 is vibrated at an arbitrary constant frequency.

Based on G _lin · dx / dt received from the amplifier 5b, the control circuit generates a drive signal for the voice coil motor for applying a force Fv proportional to the vibration speed dx / dt of the vibrating body 1 to the vibrating body 1, The generated drive signal is supplied to the voice coil motor. The voice coil motor is driven according to this drive signal and applies a force Fv to the vibrating body 1. In this way, a feedback loop is formed, and a force Fv proportional to the vibration speed of the vibrating body 1 is applied to the voice coil motor. On the other hand, the displacement signal from the capacitance displacement meter is supplied to the frequency counter as needed to detect the vibration frequency of the vibrating body 1.

The self-excited oscillation detecting means 9 compares the vibration displacement x of the vibrating body 1 with a preset threshold value based on the displacement signal supplied from the capacitance displacement meter, and based on the comparison result, It is determined whether or not the vibrator 1 vibrates (step S102). Thereby, when it is determined that the displacement x is less than the threshold value and the vibrating body 1 is not vibrating (No in step S102), a signal indicating that the gain adjusting means 5a has detected that it is not vibrating. input. Thus, the gain adjusting unit 5a increases the linear velocity feedback gain G _lin of amplifier 5b by Delta] g (step S108). This increase process is executed each time a signal indicating that it has been detected that no vibration has occurred is received.

In this way, when gradually increasing the linear velocity feedback gain G _lin, eventually, beyond the linear velocity feedback gain G _lin is the proportionality constant C _lin of viscosity term shown in the above equation (3), self-excited Oscillation occurs. That is, in the self-excited oscillation detection means 9, it is determined that the displacement x is equal to or greater than the threshold value and the vibrating body 1 has self-excited vibration (Yes in step S102). Then, a signal indicating that the self-excited vibration has been detected is input to the arithmetic unit 10.

The computing unit 10 acquires the oscillation frequency f _s from the frequency counter in response to the reception of the signal indicating that the self-excited vibration has been detected (step S104), and the acquired oscillation frequency f _s is stored in the memory. From the mass M, the linear elastic modulus k _lin of the thin film material is calculated according to the above equation (5) (step S106). Specifically, the linear elastic modulus k _lin of the thin film material is obtained by multiplying the measured value f _s of the frequency counter during self-excited oscillation by 2π and multiplying the square by the mass M.

As described above, in the linear elastic modulus measuring method and the linear elastic modulus measuring apparatus 100 according to the present embodiment, the vibration body 1 is vibrated with the vibration body 1 having a mass M in contact with the linear elastic body. By applying a force Fv proportional to the vibration speed of the body 1, it is possible to cause the vibration body 1 to vibrate by itself. Furthermore, it is possible to calculate the linear elastic modulus k _lin of the linear elastic body according to the above equation (5) based on the frequency f _s when the vibrating body 1 is self-excited and the mass M of the vibrating body 1. is there.

  Thereby, even when the damping due to the viscous stress of the measurement object is large, it is possible to measure a highly accurate and stable linear elastic modulus. Therefore, by applying the present invention to a rheometer or the like, the elastic modulus of a viscous viscoelastic body can be measured with high accuracy. In addition, for example, it is possible to realize a device that measures the hardness of a measurement object such as an internal organ with high accuracy.

In addition, in the initial stage of self-excited vibration, when the displacement x of the vibrating body 1 is below the detection limit of the displacement sensor, preliminary vibration can be applied to the vibrating body 1, so that measurement is performed without detecting displacement. It is possible to prevent the occurrence of a situation where it becomes impossible to perform the operation.
Here, in the above-described embodiment, the amplifier 5b and the driver 7 constitute feedback control means, the vibration speed calculator 4 constitutes vibration speed detection means, and the calculator 10 constitutes linear elastic modulus calculation means. .

In the above embodiment, step S102 corresponds to the step of detecting whether or not the vibrating body has self-excited, and step S108 corresponds to the step of changing the linear velocity feedback gain.
Moreover, in the said embodiment, step S104-S106 respond | corresponds to the step which calculates a linear elastic modulus.

(Modification)
In the above-described embodiment, the configuration in which the force in the direction of shear deformation is applied to the linear elastic body that is the measurement object has been described as an example, but the configuration is not limited thereto.
For example, it is good also as a structure which gives the force which deform | transforms into other directions, such as a tension | pulling direction and a compression direction, with respect to a linear elastic body.
Moreover, in the said embodiment, although the example applied to the thin film-like solid material as a linear elastic body was demonstrated, it is also possible to apply not only to a solid material but other linear elastic bodies, such as a fluid, for example.

In the above embodiment, the gain adjusting means is provided and the linear velocity feedback gain _Glin is automatically changed. However, the present invention is not limited to this configuration, and the linear velocity feedback gain _Glin may be manually changed. Good.
The above embodiments are preferable specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is described in particular in the above description to limit the present invention. As long as there is no, it is not restricted to these forms. In the drawings used in the above description, for convenience of illustration, the vertical and horizontal scales of members or parts are schematic views different from actual ones.
Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

  The present invention realizes highly accurate and stable linear elastic modulus measurement even when damping due to viscous stress is large. By applying this technology to a rheometer, it is possible to measure the elastic modulus of a viscoelastic body with high accuracy, which is useful for research and development of plastic products, foods, pharmaceuticals, and the like. It is also possible to realize a device that measures the hardness of the internal organs with high accuracy.

  DESCRIPTION OF SYMBOLS 100 ... Linear elastic modulus measuring apparatus, 1 ... Vibrating body, 2 ... Displacement sensor, 3 ... Displacement detector, 4 ... Vibration speed calculator, 5a ... Gain adjusting means, 5b ... Amplifier, 6 ... Actuator, 7 ... Driver, 8 ... Frequency detector, 9 ... self-excited oscillation detecting means, 10 ... operator

Claims (4)

A vibrating body in contact with the measurement object;
An actuator for self-exciting vibration of the vibrating body;
Vibration speed detecting means for detecting the vibration speed of the vibrating body;
Positive feedback of the vibration speed detected by the vibration speed detection means,
Fs = G _lin · (dx / dt)
Where Fs: feedback control signal
G _lin : Positive linear velocity feedback gain
x: Displacement of vibrating body
dx / dt: a feedback control means for feedback-controlling the actuator by a feedback control signal expressed by a vibration speed of a vibrating body, and a linear elastic modulus measuring method using a linear elastic modulus measuring device,
Changing the linear velocity feedback gain in the feedback control;
Detecting whether or not the vibrating body is self-excited,
Calculating a linear elastic modulus of the object to be measured based on a vibration frequency when it is detected that the vibrating body has self-excited, and a method for measuring a linear elastic modulus. In the step of calculating the linear elastic modulus,
When the mass of the vibrating body is M and the vibration frequency of the vibrating body is f _s , the linear elastic modulus k _lin of the measurement object is
k _lin = ω _s ² × M
However, ω _s : 2π × f _s
Calculated from
The method for measuring linear elastic modulus according to claim 1, wherein a vibration frequency when detecting that the vibrating body has self-excited vibration is applied as the vibration frequency f _s . The linear elastic modulus measuring device includes a displacement detecting means for detecting the displacement x of the vibrating body,
Including pre-vibrating the vibrating body at a constant frequency when the displacement x in an initial stage when the vibrating body starts self-excited vibration is below a detection lower limit value of the displacement detecting means. The method for measuring linear elastic modulus according to claim 1 or 2. A vibrating body in contact with the measurement object;
An actuator for self-exciting vibration of the vibrating body;
Vibration speed detecting means for detecting the vibration speed of the vibrating body;
Positive feedback of the vibration speed detected by the vibration speed detection means,
Fs = G _lin · (dx / dt)
Where Fs: feedback control signal
G _lin : Positive linear velocity feedback gain
dx / dt: feedback control means for feedback-controlling the actuator by a feedback control signal represented by the vibration speed of the vibrating body;
Gain adjusting means for changing the linear velocity feedback gain in the feedback control;
Self-excited oscillation detecting means for detecting whether or not the vibrator has self-excited,
Linear elastic modulus calculation means for calculating a linear elastic modulus of the measurement object based on a vibration frequency when the self-excited vibration detection means determines that it is detected that the vibrating body has self-excited vibration. A linear elastic modulus measuring device.

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